Convert CONFIG_SYS_LOAD_ADDR to Kconfig

Now that we have consistent usage, migrate this symbol to Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/configs/octeon_nic23_defconfig b/configs/octeon_nic23_defconfig
index 3d60b36..4f33187 100644
--- a/configs/octeon_nic23_defconfig
+++ b/configs/octeon_nic23_defconfig
@@ -14,6 +14,7 @@
 CONFIG_DEBUG_UART=y
 CONFIG_AHCI=y
 CONFIG_OF_BOARD_FIXUP=y
+CONFIG_SYS_LOAD_ADDR=0xffffffff80100000
 CONFIG_SYS_CONSOLE_ENV_OVERWRITE=y
 # CONFIG_SYS_DEVICE_NULLDEV is not set
 CONFIG_ARCH_MISC_INIT=y